This paper highlights the process and discusses some of the issues in the implementation of a 3-month long school-based professional development project. The participants were a group of secondary school mathematics teachers from a neighbourhood Singaporean school having a large group of minority students. The project aimed at improving the teachers’ pedagogical content knowledge by helping them to work collaboratively to analyse concepts, sequence and plan lessons, choose appropriate mathematical tasks, and so on. The project was led by an educator from the teacher training institution and a Ministry official, taking a course in leadership skills. All participating teachers completed the project and were appreciative of the experience.